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Improved Assessment of Freeze Damage to Buds Using an Equilifruit Disk

Posted: March 30, 2012

Flower mortality following Monday's low of 28 degrees F at the Penn State Fruit Research and Extension Center in Biglerville was assessed with an Equilifruit disk designed for determining how much to thin apples following fruit set. Although flower mortality on the most advanced variety, was 49%, limbs still had 4 to 10 times as many live flowers as needed for a full crop.

The variety that was most advanced was Goldrush. We randomly selected 10 limbs and counted all flowers and all dead per cluster. Flower mortality was 49%.

We measured the limbs with the Equilifruit disk and determined the desired number of fruits. When we calculated the ratio of surviving flowers to desired number of fruits, the percents were as follows:

833, 666, 522, 957, 257, 729, 1022, 390, 657, and 714.

Even in the block with the most severe freeze damage, we have many times over enough flowers to over-set a crop, although it should be noted that initial blossom cluster density was very high. We also observed that only a small fraction of spurs failed to have at least one live flower. The table below presents the findings in Goldrush and also Gala.

Growers who have an Equilifruit disk may want to use it the same way to determine the severity of flower mortality in their orchards. If you would like to obtain this new cropload assessment tool, contact Tara Baugher.

Chemical thinning will still be tricky, but we'll have time to evaluate fruit set before then.